Antenna array having an electrically controllable directivity pattern



May' 9, 1967 B. ELAcHsER ETAL ANTENNA ARRAY HAVING AN ELECTRICALLY CONTROLLABLE DIRECTIVITY PATTERN May 9, 1967 B. BLACHIER ETAL 3,319,249

ANTENNA ARRAY HAVING AN ELECTRICALLY CONTROLLABLE DIRECTIVITY PATTERN Filed Oct. l. 1963 2 Sheets-Sheet 2 f f4 f4 A, A2 A5 GNERTOR\ M/XEP M/XEA M/XER ff Pl P2 @Edf/VER R ff ,0f/nsf I l I? SH/FTES PHA 5f F] 4 SH/FTE/es fn, f'pf ffls fm f Flc-5.5

3,3%,249 Patented ll/lay 9, i967 3,319,249 ANTENNA ARRAY HAVING AN ELECTRECALLY CUNTRULILABLE Dl'RECTlWlTY PATTERN Bruno Blachier and Claude Vergnolie, Paris, France, as-

signors to CSF-Compagnie Generale de Telegraphie Sans ltil, a corporation of France Filed Oct. 1, 1963, Ser. No. 313,036 Claims priority, application France, Uct. 2, 1962, 911,020 6 Claims. (Cl. 343-100) Antenna arrays or curtains built up of an alignment of elementary sources provide high directivity, wh-ile using only easily operated elements.

It is known to cause the plane of maximum radiation of the antenna to be rotated by feeding the elementary sources with suitably adjusted phases, without mechanical rotation of the antenna. To this end, use is made of adjustable phase Shifters.

The arrangements used to this end, for example those comprising ferrites, give satisfactory results at the tranmission. But at the reception, their high noise level is a drawback which adversely affects their use with highly sensitive receivers.

The elements of the antenna can also be operated with phase Shifters, which are preadjusted, the phase variation bein-g obtained by altering the frequency of the wave.

However, this solution is difficult to apply when the received wave has a fixed frequency. Mixers are to be provided for obtaining the difference of the signal frequency and of the the frequency of a variable frequency wave, supplied by a local oscillator. This cornes back to the drawback mentioned above, for it is difficult to build mixers with very low noise.

It is an object of the present invention to provide an antenna, more particularly for the reception of signals over a wide frequency band, with an adjustable plane of maximum directivity and a very high signal-to-noise ratio.

The `antenna array according to the invention is of the type the elementary radiators of which are associated with preadjusted phase shifters, the phase shift obtained being varied by altering the frequency of the wave propagating therethrough.

This antenna is more 4particularly characterized in that (a) the phase Shifters are of two kinds, some of them receiving a variable frequency local wave, while others receive the wave resulting from the mixing of this local wave with the received signal, 4and (b) the mixers which supply this latter wave are preferably amplifiers of the parametric type including, for example, diodes, tunnel diodes, ferro-electric devices, etc., the local oscillator being the pump oscillator, whose frequency is controlled by the signal if the latter has a variable frequency.

The invention will be better understood from the following description and appended drawings, wherein:

FIG. 1 is a simplified circuit diagram of the arrangement according to the invention; l

FIG. 2 shows diagrammatically the circuit of a parametric amplifier;

FIG. 3 shows diagrammatically one embodiment of the invention;

FIG. 4 shows a further embodiment of the invention; and

FIG. 5 is an explanatory diagram of FIG. 4.

The arrangement of FIG. 1 includes n antenna elements or radiators A1, A2, A3 A11. Each radiator receives the signal at frequency fs and feeds a mixer amplifier M1 to M11. A l-ocal oscillator G supplies a local wave at a variable frequency fp. This wave is directly applied to the second input of mixer M1, through an adjustable phase shifter P1 to mixer M2, through phase Shifters P1 and P2 to mixer M3 and through phase shifte'rs P1, P2 P11 1, to mixer M11.

Receiver R receives the wave at frequency f1 which results from the mixing of waves f1, and fs in mixers M1 to M11. The wave from a mixer M11 passes through adjustable phase shifters I1 to In. One has:

Let ds be the distance between two antenna elements A1 and A1+1 and let 0 the angle of the direction of maximum directivity of the `antenna array with the normal to the array, i.e. such a direction that the signals, respectively received by receiver R from the elementary radiators A1 to A11 through mixers M1 M11, and phase shifters I1 In are all in phase.

The phase difference between the waves received by antennas A1 and antenna A1 1 is:

2rd, taiwhere xs is the operating Wavelength.

The phase at the output of a mixer M1 is the difference between the phase e111 of the wave which has propagated through phase Shifters P1 to P1 1 and the phase o1 of the wave propagating from antenna A1. The wave from antenna A1 1 arriving to the receiver is therefore shifted in phase with respect to the wave from antenna A1 by -Sin 6 21rd sin 0 A909 S Preferably, phase shifters P and I are transmission lines, line P all having a length lp and lines I a length I1.

Relation 3 can then be written:

where n is a whole member, and c is the velocity of light. -This relation can be written, taking Relation 1 into account:

l1-d sin 9 'n.c

This relation gives the pump frequency fp to be used for the reception of a wave of frequency fs propagated in a direction 0, with l1 and ID chosen once one for all.

The lengths IS and l1 may be chosen to secure optimum performance of the amplifier phase Shifters.

This statement can be justified by a very simple calculation. The case will be described in which mixers M are parametric amplifiers comprising non-linear capacitors, a similar calculation being possible with a nonlinear inductance or resistance elements (for example, a tunnel diode biased close to peak tunnel current).

FIG. 2v shows an equivalent circuit of a parametric amplifier performing the function of the mixers shown in FIGURE 1.

The signal input circuit, the output or idler circuit, and the pump circuit are coupled to each other -by a nonlinear capacity.

The input and pump circuits include respectively voltage sources VS and V11, resistances Rs and R1J and inductance coils Ls and Lp used to tune these circuits respectively to frequencies Fs and Fp. The Q-factors of these circuits wil be designated by Qs and Q11. The idler circuit is tuned to a frequency F1=F11Fs by an inductance a) coil Ll with a Q-factor Qi and includes a lead resistance Ri. Under the action of the pump, capacitor C changes its value from C to:

If a signal of frequency fs is injected in the'signal input circuit, a signa-l is collected in the idler circuit having a frequency f1=fp fs- It is assumed that the signal has an instantaneous frequency fs, the pump a variable instantaneous frequency fp, the pump a variable instantaneous frequency f, the resulting idler frequency being f1.

Setting:

Fs, Fp and F1 being the central frequencies to which the three circuits are tuned and Afs, Afp and Afl being the respective instantaneous frequency shifts from said central frequencies.

It is known that, disregarding the diode internal resistance, the conversion gain of a parametric amplifier, that is to say that the ratio of the power collected in resistance R1 to the maximum power available at the signal input,

can be written:

FB a G f. 1- 2+ Q.e.-Q.f. 2 6) where a is a factor characteristic of the amplifier. Thus:

AC 2 ol-'Qs'Qx 2Co Formula 5 shows that the conversion gain is maximum when a is not close to 1, and

Condition 9 shows that the relative mistuning of frequencies fs and fi must in this case be mutually proportional to secure optimum performance of the mixer amplifiers, when fs varies. This relation, which is very simple in the case of simple tank circuits, may be much more complex in the case of actual circuits, but it gives a fair account of the physical phenomena.

The two following cases of operation of the system according to the invention will be considered:

(a) Reception in a fixed direction (for the sake of simplicity, 0 will be ltaken lequal to 0) of a signal at an instantaneous frequency fs deviatin-g by an appreciable amount Afs from the central tuning F5 of the diode signal circuit.

The following calculation will show that, yfor given parametric diodes, lp and l can be chosen to secure optimum gain and minimum noise figure over a relatively wide frequency band F=F5iAFs- Relation 3a becomes:

(Fri-MDN =(F1l-Af1)l1+n0 (10) where 0:0.

This relation must of course apply when Afp and Af have the value 0, i.e. in the middle of the bon-d, hence:

subtracting term by term Equation l1 from Equation 10, one may write:

Equations l1 and 12 with two unknowns li and lp give the relative phase shifts to be applied to phase shifters I and P, in order to obtain, in the case of given parametric diodes, the widest possible reception frequency range with a constant gain:

Replacing lp and l, by their values from Equation 13 and taking into consideration the fact that dfp=dfh then:

fade F E dfD---s Fp Fssm (15) In order to remain within maximum amplitude conditions, when the direction of maximum d'ireotivity is varied by a given value 0, the pump frequency fp has to be varied by a small amount dfp, so that n has to be large. But there is a restriction due to thev antenna bandwidth which decreases as n. increases.

FIG. 3 shows an embodiment of the invention.

In this figure the same references designate the same parts as in FIG. l, but now the receiver R is tuned to the signal frequency fs.

The system includes in addition: A converter M feeding the receiver R for converting the frequency f1 to the signal frequency fs.

A wavemeter O Ifor measuring the frequency fs and extracting a voltage Vs proportional to fs.

An angle computer N supplying a voltage V9 proportional to 0, the angle to be explored.

A computer C which receives the voltage Vs, V6 and delivers a voltage Vp which controls the generator G, the latter delivering a voltage fp in accordance with Relation 4. This is a control system of the phase-lock type which will require search scanning to lock onto an unknown variable frequency. A control for the angle computer can also lbe envisaged to enable the antenna to follow the direction 0M of maximum reception. To this end a feedback connection is provided between the receiver R and a control input of computer N.

FIG. 4 shows one other embodiment of the invention.

Source I transmits a frequency spectrum as shown in FIGURE 5, the medium frequency of which is a frequency F. A square wave modulated single side band generator may be used for generating said spectrum.

The Ifrequencies fpn are equally spaced in said spectrum.

The device shown in FIGURE 4 allows the reception in directions 0n satisfying the following equations:

(FIG. 5). The reception along one of said `directions is obtained by tuning the receiver to the corresponding idler frequency.

Of course, the invention is not limited to the embodiments shown and described which were given solely by way of example.

What is claimed is:

1. An antenna for ultra-high frequency energy signals comprising in combination: an array of elementary radiators equally spacedy along at least one straight line; a plurality of parametric amplifiers having respective rst inputs connected to said radiators, second inputs and outputs; a source of a pumping energy; a first plurality of phase shifters having the same predetermined electrical length, connecting in cascade said second inputs to said pumping source; a receiver tuned to an idler frequency of said parametric amplifier; and a second plurality of phase shifters having a second predetermined electrical length connecting in cascade said outputs to said receiver.

2. An antenna for ultra-high frequency signals comprising in combination: an array of radiating elements equally spaced along at least one straight line; a plurality of mixers having respective first inputs connected to said elements, and second inputs and outputs; a source of local energy; a first plurality of phase shifters having the same predetermined electrical length, for connecting in cascade said second inputs -to said local source; a receiver tuned at the output frequency of said mixer; and a second plurality of phase shifters having a second predetermined electrical length for connecting in cascade said outputs to said receiver.

3. An antenna for ultra-high frequency energy signals comprising in combination: an array of elementary radiators equally spaced along at least one straight line; a plurality of parametric amplifiers having respective first inputs connected to said radiators, second inputs and outputs; a source of a pumping energy; a first plurality of phase shifters having the same predetermined electric length, connecting in cascade said second inputs to said pumping source; a receiver tuned to the signal frequency and comprising a converter tuned to an idler frequency of said parametric amplifier; a second plurality of phase shifters having a second predetermined electrical length connecting in cascade said outputs to said receiver; and means controlled by said signal Ifrequency for controlling the frequency of said pumping energy.

4. An antenna for ultra-high frequency energy signals comprising in combination: an array of elementary radiators equally spaced along at least one straight line; a plurality of parametric amplifiers having respective first inputs connected `to said radiators, second inputs and outputs; a source of a pumping energy; a first plurality of transmission lines having the same predetermined electrical length, connecting in cascade said second inputs to said pumping source; a receiver tuned to an idler frequency of said parametric amplifier; and a second plurality of transmission lines having a second predetermined electrical length connecting in cascade said outputs to said receiver.

5. An antenna for ultra-high frequency energy signals comprising in combination: an array of elementary radi ators equally spaced along at least one straight line; a plurality of parametric amplifiers having respective first inputs connected to said radiators, second inputs and outputs; a source of a pumping energy; a first plurality of transmission lines having ther same predetermined electrical length, connecting in cascade said second inputs to said pumping source; a receiver tuned to the signal frequency and comprising a converter tuned to an idler frequency of said parametric amplier; and a second plurality of transmission lines having a second predetermined electrical length connecting in cascade said outputs to said receiver; a wavemeter coupled to said converter for measuring the signal frequency and for delivering a first voltage proportional to said signal frequency; first cornputer means receiving a magnitude proportional to the angle of a predetermined directivity, and having an output for delivering a voltage proportional to said angle; second computer means Ifor receiving said first and second voltage and lfor delivering a control voltage; and means for delivering said control Voltage to said source of pumping energy.

6. An antenna for ultra-high frequency energy signals comprising in combination: an array of elementary radiators equally spaced along at least one straight line; a plurality of parametric amplifiers having respective first inputs connected to said radiators, second inputs and outputs; a source of a pumping energy, said source simultaneously generating a plurality of pumping frequencies equally spaced in a predetermined frequency band; a first plurality of transmission lines having the same predetermined electrical length, connecting in cascade said second inputs to said pumping source; a receiver tuned to an idler frequency of said parametric amplifier; and a second plurality of transmission lines having a second predetermined electrical length connecting in cascade said outputs to said receiver.

References Cited bythe Examiner UNITED STATES PATENTS 2,247,666 7/1941 Potter 343-10016 2,719,223 9/1955 Van der Ziel et al. 330-4.5 3,048,783 8/1962 War-ren et al. 330-4.5 3,118,113 1/1964 Ferrar et al, 330-4.5 X 3,202,992 8/196-5 Kent et al. 343-1006 RODNEY D. BENNETT, Primary Examiner. CHESTER L. JUSTUS, Examiner.

H. C. WAMSLEY, Assistant Examiner. 

1. AN ANTENNA FOR ULTRA-HIGH FREQUENCY ENERGY SIGNALS COMPRISING IN COMBINATION: AN ARRAY OF ELEMENTARY RADIATORS EQUALLY SPACED ALONG AT LEAST ONE STRAIGHT LINE; A PLURALITY OF PARAMETRIC AMPLIFIERS HAVING RESPECTIVE FIRST INPUTS CONNECTED TO SAID RADIATORS, SECOND INPUTS AND OUTPUTS; A SOURCE OF A PUMPING ENERGY; A FIRST PLURALITY OF PHASE SHIFTERS HAVING THE SAME PREDETERMINED ELECTRICAL LENGTH, CONNECTING IN CASCADE SAID SECOND INPUTS TO SAID PUMPING SOURCE; A RECEIVER TUNED TO AN IDLER FREQUENCY OF SAID PARAMETRIC AMPLIFIER; AND A SECOND PLURALITY OF PHASE SHIFTERS HAVING A SECOND PREDETERMINED ELECTRICAL LENGTH CONNECTING IN CASCADE SAID OUTPUTS TO SAID RECEIVER. 